Interpretive Summary: Reducing emissions of fumigants is critical to minimizing detrimental impact to the environment, and to ensure practicable use of alternative fumigants for agricultural production. Cost-effective practices in reducing fumigant emissions are mostly needed. This study tested if surface water applications can effectively reduce emissions of 1,3-dichloropropene (1,3-D) in comparison with plastic tarp treatments in soil column experiments . Results show that surface water applications were as effective or even more effective than using standard plastic tarp to reduce 1,3-D emissions. As using water is less expensive than plastic tarp, surface water application practices may be developed to control fumigant emissions.

Technical Abstract:
High emission rates of fumigants from soil increase the risk of detrimental impact on workers, bystanders and the environment, and jeopardize future availability of fumigants. Efficient and cost-effective approaches to minimize fumigant use are needed. This study evaluated the potential of surface water application (or water seal) to reduce 1,3-dichloropropene (1,3-D) emission from soil (Hanford sandy loam) columns. Treatments included dry soil (control), initial water application (8 mm water just before fumigant application), initial plus a second water application (2.6 mm) at 12 h after fumigation, initial plus two water applications (2.6 mm each time) at 12 h and 24 h after application, standard high density polyethylene (HDPE) tarp, initial water application plus HDPE, and virtually impermeable film (VIF) tarp. Emissions from the soil surface and distribution of 1,3-D in the soil-gas phase were monitored for two weeks. Each water application abruptly reduced 1,3-D emission flux, which rebounded, however, over a few hours. Peak emission rates were substantially reduced, but total emission reduction was small. Total fumigant emission was 51% of applied for the control, 46% for initial water application only, and 41% for the three intermittent water applications with the remaining water treatment intermediate. HDPE tarp alone resulted in 45% emission, while initial water application plus HDPE tarp resulted in 38% emission. The most effective soil surface treatment was VIF tarp (10% emission). Surface water applications can be more effective and less expensive than standard HDPE tarp. High frequency of water applications is required to substantially reduce emissions.